Birthday timeshift of 1 day

[twickle]

Hello,

when i'm entering a birthday to the birthday field in outlook 2003,, then zimbra shows in the web ui that birthday with 1 day timeshift.
(Zimbra 4.5.6)

Example:

Outlook: 30.11.1978
Zimbra shows: 29.11.1978

Might that matter has anything to do with time zone settings?
I have GMT+1 with automatic change between summer and winter time. (without that setting all the mails were time shifted for one hour)

Thanks,
Thomas